VIII, B, 4 Walker and Sellards: Entamoebic Di/sentery 315 



various cells, including red blood corpuscles, of its host. On 

 the other hand, the cytoplasm of Entamoeba coli is more granular 

 in appearance (Plate I, fig. 3). A hyaline ectoplasm is apparent 

 only in the pseudopods of the motile entamoeba. The cytoplasm 

 of coli more often contains bacteria, starch and proteid grains, 

 and other debris from the faaces than cells from the body of its 

 host. The absence from the cytoplasm of red blood corpuscles 

 and other cells of its host may result rather from the fact that 

 coli is a strict commensal and is more often found in non- 

 dysenteric stools than from its incapacity to ingest red blood 

 corpuscles. 



Nucleus. — The nucleus of Entamoeba histolytica is usually in- 

 distinct in the motile organism, especially if it be actively motile 

 or much vacuolated. In the latter case it is sometimes impos- 

 sible to distinguish the nucleus from the vacuoles. In stained 

 preparation the nucleus of histolytica is seen to possess a thin 

 membrane and to be relatively poor in chromatin. This chro- 

 matin is distributed as a thin peripheral layer or as scattered 

 granules about the inner surface of the nuclear membrane, with 

 a few granules scattered in the network of the nonrefractive, 

 nonstainable nucleoplasm (Plate I, fig. 5). This type of nucleus 

 is characteristic of histolytica found in stools in acute dysentery 

 that consist exclusively of mucus and blood. In stools of chronic 

 cases of dysentery that consist of more or less mucus and blood 

 mixed with fsecal matter, the so-called "tetragena" type of nucleus 

 is commonly met with. This type of nuclear structure contains 

 more chromatin than the preceding type, and the chromatin has 

 a characteristic arrangement. It is distributed partly as a more 

 or less extensive but loose layer, which frequently shows radial 

 projections, about the inner surface of the nuclear membrane, 

 and partly as a loose central karyosome of varying structure. 

 This karyosome consists typically of a central granule, the 

 "centriol," surrounded by a clear halo that is bounded by a layer 

 of chromatin granules (Plate I, fig. 6). All intermediate stages 

 between the typical histolytica and the "tetragena" types of 

 nuclei are to be observed in dysenteric stools. On the other 

 hand, the nucleus of Entamoeba coli is distinctly visible in the 

 living and motile entamoeba as a heavy refractive ring. It con- 

 sists of a nuclear membrane and a relatively large amount of 

 chromatin which is arranged as a heavy, dense, continuous or 

 broken layer about the inner surface of the nuclear membrane 

 and sometimes also in a small, central, dense karyosome. The 

 interior of the nucleus consists of a nonrefractive, nonstainable 



